Prosecutorial discretion exists throughout the criminal justice system but plays a particularly significant role for environmental crime. Congress made few distinctions under the environmental laws between acts that could result in criminal, civil, or administrative enforcement. As a result, there has been uncertainty about which environmental violations will result in criminal enforcement and persistent claims about the over-criminalization of environmental violations. To address these concerns – and to delineate an appropriate role for criminal enforcement in the environmental regulatory scheme – I have proposed that prosecutors should reserve criminal enforcement for violations that involve one or more of the following aggravating factors: (1) significant environmental harm or public health effects; (2) deceptive or misleading conduct; (3) operating outside the regulatory system; or (4) repetitive violations. By doing so, prosecutors can focus on violations that undermine pollution prevention efforts and avoid targeting defendants acting in good faith or those who committed technical violations of the law. This Article presents the results of an empirical study to determine how often those factors were present in cases investigated by EPA that resulted in criminal charges from 2005-10. My empirical research demonstrates that prosecutors charged violations involving these aggravating factors for nearly every defendant prosecuted over a six-year period. Indeed, most defendants engaged in conduct that involved multiple aggravating factors. These findings suggest that prosecutors are exercising their discretion reasonably under the environmental laws and provide empirical evidence that should inform our understanding of the role of criminal enforcement and lessen concerns about over-criminalization.